Modern wireless communications devices often support signal transmission and reception over multiple radio frequency bands, using one of several distinct communications protocols or standards. For example, a single cellular phone may communicate using any or all of the WCDMA, CDMA, GSM, EDGE, and LTE standards for cellular telephony, over any frequency bands allotted for such communications.
In a communications device, radio-frequency (RF) circuitry is typically provided to upconvert a baseband signal to a particular radio frequency band for wireless transmission. The RF circuitry supporting each frequency band and/or wireless standard typically must satisfy different design constraints. For example, for certain modulation formats, it may be advantageous to use a linear architecture for upconverting the baseband signal, e.g., in-phase and quadrature components of the baseband signal are multiplied with corresponding in-phase and quadrature components of a local oscillator signal. Alternatively, for other modulation formats, it may be advantageous to use a polar architecture for upconverting the baseband signal, e.g., a single baseband signal having real amplitude is multiplied with a local oscillator signal having variable phase.
To accommodate multiple modulation formats, it would be desirable to provide a communications device capable of operation in both linear and polar modes, while minimizing unnecessary replication of component circuitry.